It has a trinocular head, the tube is to mount a camera if you choose. The opening should be capped when not in use so dust and dirt stays out. 100x objectives need immersion oil on the slide to focus. Youtube should have plenty of videos how to use the oil.

For cleaning look here http://www.well.ox.ac.uk/_asset/file/the-clean-microscope.pdf

A general tip, I recommend getting a box of these https://www.amazon.com/Kimtech-Science-KimWipes-Delicate-Wipers/dp/B0013HT2QW/ref=sr_1_4?ie=UTF8&qid=1543119000&sr=8-4&keywords=Microscope%2BWipes&th=1&psc=1. I use them to clean up glass surfaces on the scope and even sunglasses, but should be used with a lense cleaner and in proper process.